Paperboard is used in various packaging applications. For example, aseptic liquid packaging paperboard is used for packaging beverage cartons, boxes and the like. Therefore, customers often prefer paperboard having a generally smooth surface with few imperfections to facilitate the printing of high quality text and graphics, thereby increasing the visual appeal of products packaged in paperboard.
Manufacturers have attempted to smooth the surface of paperboard by coating the entire surface of the paperboard with a basecoat comprised of various pigments, such as clay, calcium carbonate, TiO2 and the like, then overcoating this base with a second and sometimes even a third coating, which is generally referred to as a topcoat. It was discovered that high quantities of relatively fine pigment particles applied to the surface of paperboard provided a smoother surface without sacrificing bulk. Indeed, it has been understood that the more pigment particles applied to the surface of the paperboard the better the resulting smoothness. However, the use of relatively high quantities of pigments substantially increases the cost of preparing smooth and highly printable paperboard.
Accordingly, those skilled in the art continue with research and development efforts in the field of paperboard coating.